Alterations in Blood Flow

Circulatory System: * Primary function: transport of oxygen and nutrient and removal of metabolic waste products * Requires complex circuitry of vessels powered by heart

General Mechanisms That Alter Flow: * Flow reduction in systemic circuit creates ischemia, leading to hypoxia * Flow reduction in venous system alters waste removal and increases systemic pressure * Venous engorgement or venous obstruction * Flow reduction in lymphatic system causes edema * Changes to lymphatic vessels and lymph circulation * Blood vessel obstructions * Blood vessel structural alterations

Lymphatic Vessels: * Lymphatic circulation overwhelmed when changes in capillary or interstitial oncotic pressures increase filtration, or when fluid movement at capillary bed is impaired * Causes edema * Causes wide variety of conditions * Lymphedema- lymphatic flow alteration due to impairment in lymph circulation

Blood Vessel Obstructions: * Alteration of blood flow may involve impedance of arterial or venous flow * Some obstructions specific to arterial or venous * Others form on both sides * Will now cover those that affect arteries and veins- specific later * Thrombus= blood clot attached to vessel wall * Thromboembolus- detached thrombus * Develop where conditions activate hemostasis * Different triggers for arteries and veins * Shock can lead to thrombi * Impaired metabolism and blood stasis * Arterial thrombi- 2 threats: * Occlusion of artery * Thromboembolus causing occlusion at distant size * Venous thrombi- cause edema and can embolize * Embolism- obstruction of a vessel by an embolus * Embolus- bolus of matter circulating in the bloodstream * Many types of material can create embolus * Source of embolus determines which circuit will be occluded * Cause ischemia or infarction * Thromboembolism- dislodged thrombus * Air embolism- undissolved air * Amniotic fluid embolism- forced into mother through uterine wall * Bacterial embolism- aggregates of bacteria * Fat embolism- trauma to long bones * Foreign matter- enters due to trauma, IV, or intra-arterial lines * Vasospasm- sudden involuntary constriction of arterial smooth muscle that obstructs flow * Inflammation-vasculitis= inflammation of intima or artery * Phlebitis- inflammation of intima of vein * Mechanical compression- external forces altering blood flow

Structural Alteration of Blood Vessels * Valvular incompetence- when intimal folds of venous valves are damaged * Varicose veins are chronic venous insufficiency * Arteriosclerosis/Atherosclerosis * Narrows arterial lumen and limits ability to dilate * Aneurysms- localized dilation of arterial wall * Arteriovenous fistulas (AVF)- abnormal communication between arteries and veins * Most common type is AVM * Arteritis- Thromboangitis obliterans * Raynaud Syndrome * Aneurysms * Acute Arterial Occlusion

Arteritis * Thromboangitis obliterans- Buerger Disease * Inflammatory disease of peripheral arteries * Inflammatory lesions accompanied by thrombi and vasospasms * Can occlude and obliterate small and medium arteries in feet and hands

Raynaud Syndrome * Attacks of vasospasms in small arteries and arterioles of fingers and toes * Raynaud phenomenon- same symptoms, different cause * Phenomenon is secondary to systemic diseases * Raynaud syndrome (disease)- primary vasospastic disorder of unknown origin

Aneurysms * Localized arterial dilation * Many causes * Most common- cerebral, thoracic, aortic * True aneurysms- all three tunics * Subdivided into saccular or fusiform * False aneurysms- at least one tunic unaffected * Dissecting aneurysm- tear in arterial wall creates blood flow channel * Non-dissecting may be asymptomatic * Dissecting aortic aneurysms- sudden, severe tearing pain in back and abdomen

Acute Arterial Occlusion * When embolism lodges in major artery * No arterial flow to extremity * No surgery- gangrene * Symptoms- 6 P’s * Pallor * Parasthesis * Paralysis * Pain * Pulseless * Polar

Alterations in Venous Flow * Valvular Incompetence * Varicose veins * Chronic venous insufficiency * Deep vein thrombosis

Valvular Incompetence * Causes venous insufficiency * Varicose veins- superficial valvular incompetence * Chronic venous insufficiency- deep vein valvular incompetence * Causes of incompetence: * Valvular over-stretching due to excessive venous pressures * Backflow * Standing for long periods, obesity, pregnancy * Thrombi can promote valve obstruction

Varicose Veins * Veins in which blood has pooled * Typically- saphenous veins- distended, tortuous and palpable * Trauma damages one or more valves or valvular incompetence * Surrounding tissue becomes edematous * Can progress to chronic venous insufficiency

Chronic Venous Insufficiency * CVI- inadequate venous return over long period; chronic pooling of blood in veins of lower extremities * Pathological changes due to ischemia * Marked edema of feet and ankles * Sluggish circulation in extremities- venous stasis ulcers- susceptible to infection

Deep Vein Thrombosis * Common condition- outpatient and hospital setting * 26% of all hospitalized patients- higher for certain disorders * Outside hospital – genetics and prolonged limb dependency * Primarily lower extremity * Promoted by: * Venous stasis * Venous endothelial damage * Hypercoagulabe states * Thrombus may obstruct venous flow * Untreated- high risk of embolization

Alterations in Lymphatic Flow * Lymphedema when normal flow of lymph is obstructed or altered * Primary- due to congenital absence or decreased numbers of lymphatics * Also obstruction of thoracic duct of cisterna chili * Secondary- surgical removal of lymph nodes of destruction of lymphatcis